title: Unusual edge effect in patch testing with silver nitrate.
abstract: Silver nitrate is a widely used substance and has been applied topically for cauterizing bleeding and healing wounds. In the past it has even been used to mark patch test sites, when no one knew that the substance itself might be a sensitizer. However, there are also toxic reactions to that substance. We report a case in which a positive "edge effect" at the periphery of the patch test site could be shown. It can be explained by the unequal distribution of patch test solutions in the different patch test systems with a concentration at the rim. Distinguishing between allergic and toxic reactions may be difficult when an edge effect occurs. Therefore, in certain rare cases a biopsy or a lymphocyte transformation test might be of help.
authors.affiliation: Department of Dermatology, University Hospital Zurich, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Iliev
authors.forename: P
authors.initials: P
authors.lastname: Elsner
mesh_terms: D000485:Allergens; D000891:Anti-Infective Agents, Local / Q000009:adverse effects*; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000473:pathology; D003937:Diagnosis, Differential; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000009:adverse effects*; D012835:Silver Nitrate / Q000009:adverse effects*; D012867:Skin / Q000473:pathology
chemical_list: D000485:Allergens; D000891:Anti-Infective Agents, Local; D012835:Silver Nitrate